Fusarium culmorumproduces NX-2 toxin simultaneously with deoxynivalenol and 3-acetyl-deoxynivalenol or nivalenol (submitted to Toxins)

Abstract

AbstractFusarium culmorumis a major pathogen of grain crops. Infected plants accumulate deoxynivalenol (DON), 3-acetyl-deoxynivalenol (3-ADON), or nivalenol (NIV), which are mycotox-ins of the trichothecene B group. These toxins are also produced byF. graminearumspecies complex. New trichothecenes structurally similar to trichothecenes B but lacking the carbonyl group on C-8, designated NX toxins, were recently discovered in atypical isolates ofF. graminearumfrom North America. Only these isolates and a few strains of a yet to be characterizedFusariumspecies from South Africa are known to produce NX-2 and other NX toxins. Here we report that among 20F. culmorumstrains isolated from maize, wheat, and oat in Europe and Asia over a period of 70 years, 18 strains produced NX-2 simultaneously with 3-ADON and DON or NIV. Rice cultures of strains producing 3-ADON accumulated NX-2 in amounts corresponding to 2-8% of 3-ADON (1.2 - 36 mg/kg). A strain producing NIV accumulated NX-2 and NIV at comparable amounts (13.6 and 10.3 mg/kg, respectively). InF. graminearum, producers of NX-2 possess a special variant of cytochrome P450 monooxygenase encoded byTRI1that is unable to oxidize C-8. InF. culmorum, producers and non-producers of NX-2 possess identicalTRI1; the reason for the production of NX-2 is unknown. Our results indicate that production of NX-2 simultaneously with trichothecenes B is a common feature ofF. culmorum.Key resultIsolates ofFusarium culmorumobtained from different hosts at different locations over several dec-ades produced NX-2, which is a type A trichothecene structurally related to 3-ADON.